Method and system for latency measurement in communication systems

ABSTRACT

Described is a method and system for latency measurement in communication systems. The method comprises: determining, by a first communication device, a power-management state of a second communication device; transmitting, by the first communication device, one or more packets to the second communication device over a communication link, the one or more packets to be received by the second communication device while in the power-management state; receiving, from the second communication device over the communication link, one or more response packets in response to the one or more packets; and determining a latency of the communication link when the second communication device is in the power-management state based on the one or more packets and the one or more response packets.

CLAIM OF PRIORITY

This application is a U.S. National Phase application under U.S.C. § 371of International Application No. PCT/US2012/059395, filed Oct. 9, 2012,entitled “METHOD AND SYSTEM FOR LATENCY MEASUREMENT IN COMMUNICATIONSYSTEMS”, the entire contents of which are incorporated herein byreference.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

TECHNICAL FIELD

The subject matter described herein relates generally to the field ofcomputing, and more particularly, to a method and system forcommunication link measurement and/or diagnostics, including latencymeasurement and connectivity diagnostics.

BACKGROUND

Monitoring performance of a communication link is used, for instance,for proactively addressing and preventing user complaints, for decidingwhen to upgrade hardware associated with the communication link, fordeciding when to trigger an optimization algorithm to optimize thecommunication link, for verifying that the optimization algorithm hasindeed resulted in improved performance, etc.

The term “performance” herein refers generally to network throughput(e.g., TCP/UDP), latency, jitter, connectivity, error rates, powerconsumption, transmit power, etc. Improving performance of thecommunication system includes increasing throughput, reducing error rateand latency, improving jitter, power consumption, etc. for thecommunicating system. Monitoring performance generally refers todetermining and/or calculating one or more of the above performanceparameters associated with the communication link. The term “TCP” standsfor transmission control protocol. The term “UDP” refers to userdatagram protocol.

Communication system performance can be evaluated using traditionaltesting software applications such as iperf, netperf, ttcp, etc. Suchsoftware applications need to be installed on at least two communicationdevices where the software application on one communication devicegenerates and transmits test data to the other communication device, andwhere the software application on the other communication devicereceives the test data.

After transmitting and receiving the test data, statistics of the testdata transportation is evaluated to assess the performance of thecommunication link between the two communication devices. Testing of acommunication system or network to gauge its performance via suchtraditional testing software applications requires compatible softwareapplications to be installed or to be available at both communicationdevices that form the communication link.

For example, a user with a laptop visits a performance testing web site,and subsequently a testing software application is loaded to the user'sweb browser. Then the performance between the laptop and a server in theinternet is measured using the testing software application that wasalready available at the server.

In some cases, however, it can be difficult, if not impossible, to havetesting software applications available at both communication devicesthat are at the ends of the communication link of interest. Forinstance, when a network manager is interested in initiating aperformance measurement from a Wi-Fi Access Point (AP) to a smart-phone,the network manager does not have any means to install a softwareapplication to the smart-phone. Therefore, the network manager cannotinitiate performance measurement between the Wi-Fi AP and thesmart-phone. In general, it is difficult to have applications availableat communication devices coupled to a network or to initiate user-sideinstallation of software applications as a network manager.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure will be understood more fully from thedetailed description given below and from the accompanying drawings ofvarious embodiments of the disclosure, which should not be taken tolimit the disclosure to the specific embodiments, but are forexplanation and understanding only.

FIGS. 1a-1c illustrate communication networks which are operable todetermine communication link metrics, according to embodiments.

FIG. 2 is a flowchart for determining the latency of a communicationlink, according to one embodiment.

FIG. 3 is a flowchart for determining the latency of a communicationlink, including transmitting one or more initial packets to acommunication device over a communication link, according to oneembodiment.

FIG. 4 is a flowchart for determining the latency of a communicationlink, including retrieving status information of a communication device,according to one embodiment.

FIG. 5 is a flowchart for determining a connectivity metric of acommunication link, according to one embodiment.

FIG. 6 is a processor-based system in accordance with which embodimentsmay operate, be installed, integrated, or configured.

FIG. 7 illustrates an exemplary architecture in which embodiments mayoperate, be installed, integrated, or configured.

DETAILED DESCRIPTION

Described herein are systems and methods for determining communicationlink metrics.

Measuring or determining metrics for communication links, includinglatency and connectivity diagnostics, can provide data that is usefulfor a variety of applications. For example, determining the latencyand/or connectivity diagnostics for a communication link can be usedfor: identifying causes of performance issues, proactively addressingand/or preventing user complaints, determining when to upgrade hardwareand/or software, determining how and/or when to perform optimizationsfor a communication link or communication devices, and/or verifyingoptimizations resulted in improved performance.

Latency is a communication link metric that can be important inapplications including video streaming (e.g., Internet Protocoltelevision (IPTV)), real time applications (e.g., Voice over IP (VoIP),online gaming, and other real time applications), applications on mobiledevices, and other applications impacted by latency.

In some communication systems in which latency can be measured, acommunication device will enter a sleep state if there is no activity toconserve power. A device in a sleep state may not respond immediately toincoming packets, which can impact latency measurements. Wi-Fi stations(e.g., smart phones, mobile devices, and other client devices) are anexample of communication devices that can enter a sleep state. Delays inresponses caused by sleep states can add significant bias and randomnessto latency test results (because, for example, the wait time due to thesleep state dominates the round trip time (RTT) of packets).

Connectivity is another communication link metric, and can indicate thestability of a communication link Examples of applications in whichconnectivity diagnostics can be useful include: video streaming, realtime applications, applications on mobile devices, and otherapplications impacted by connectivity issues.

Video streaming applications can require large average throughputbetween the communication devices. Connectivity issues can result inpacket overflows within the internal buffers, which can causeinstability to the communication device software.

Real time applications such as VOIP can require constant bit rate (CBR)streaming between the communication devices, and connectivity issues cancreate loss of packets or latency jitters that are detrimental to CBRapplications.

Mobile devices (e.g., smart phones, netbooks, and other mobile computingdevices) can have multiple communication interfaces (e.g., Wi-Fi, 3G/4G,and other communication interfaces) and have the ability to switchbetween the different networks. Link connectivity issues in one network(e.g., Wi-Fi) could cause the communication device to automaticallyswitch to the other network (e.g., 3G or 4G) without the knowledge ofthe user. The user, when using broadband, could be exhausting his mobiledata usage, while thinking that he is actually using the unlimited Wi-Fiaccess network. Additionally, frequent link disconnections andreconnections can result in network delays that have a direct impact onuser applications.

Embodiments include systems and methods for determining latency ofcommunication links between communication devices, at least one of whichincludes power-management features. Power-management features includesoftware and/or hardware to enable states of greater or lesser powerusage corresponding to varying levels of activity. For example,power-management features enable one or more “sleep states” whichcorrespond to reduced activity levels, and one or more “non-sleepstates” which correspond to higher or normal operating activity levels.In one embodiment, the sleep state of a communication device is detectedand/or avoided when measuring latency of a communication link. Forexample, an agent (e.g., an agent within one communication device orexternal to the communication device) can issue commands to a secondcommunication device to measure the latency, and also provide ways todetect and/or avoid the second device's sleep state. In one suchembodiment, latency of the communication link can be measured withoutrequiring availability of testing software applications on both sides ofa communication link.

The sleep state of a communication device can be avoided with activeprobing. The term “active probing” generally refers to testing of acommunication network by sending test pattern/data over the network fromone communication device to another communication device. In oneembodiment, active probing involves an agent which injects generatedtraffic to a target communication device. For example, in oneembodiment, an agent in a Wi-Fi Access Point injects background trafficinto layer 2 targeting a station. Although the injected traffic will berejected from the upper layer of the station, the traffic will reach theWi-Fi layer of the station and keep the station in a non-sleep state, orcause the station to exit a sleep state. In one embodiment, the agentissues latency measuring commands (e.g., ping commands, TCP synch/resetcommands, and/or other latency measuring commands) after and/or duringthe injected traffic. In one embodiment, the agent measures the roundtrip time (RTT) of the latency measuring packets and correspondingresponse packets. In one embodiment, constant traffic prevents thedestined communication device from going into a sleep state while theagent measures latency.

According to one embodiment, the volume of the injected traffic can beadjusted to keep and/or cause a communication device to be in anon-sleep state. In one such embodiment, the volume of injected trafficdoes not cause the link to be excessively busy or overwhelmed with theinjected traffic. Limiting the injected traffic to prevent flooding ofthe communication link can prevent substantial bias in the latencymeasurements caused by the injected traffic. Once the desired latencymeasurements are obtained, the agent can stop injecting traffic. In oneembodiment, measuring latency during and/or immediately after injectedtraffic eliminates inaccuracies in latency measurements caused byunpredictable wait times due to power-management states.

In one embodiment, an agent issues latency test commands successivelywithout a wait time between them. The successive latency test commandsresult in a continuous stream of packets and prevent the targetcommunication device from going into a sleep state. In one suchembodiment, if the target communication device is in a sleep state whenthe agent issues the latency test commands, the target communicationdevice may not transition to a non-sleep state prior to receiving a fewpackets (e.g., 2 packets, 3 packets, or more packets). The agent cancheck the status of the target communication device to determine if agiven latency measurement is made when the target communication deviceis in a sleep state or a non-sleep state. For example, the agent canread the current status information data field before a latency probingpacket, after a latency probing packet, or before and after a latencyprobing packet. In one embodiment, a Wi-Fi access point has informationon the current status of each station connected to the Wi-Fi accesspoint (e.g., whether the station is in a sleep state, in a non-sleepstate, and/or other status information related to the station) due tothe design of systems as specified in the IEEE 802.11 standard.Therefore, status information can be used to filter out the measurementsand/or to interpret measurements accurately.

In one embodiment, an agent injects initial traffic (e.g., to wake up atarget communication device or to keep the target communication devicein a non-sleep state), and checks the status of the target communicationdevice (e.g., reads the status information data field). Thus, inembodiments, the agent can determine when a target communication deviceis in a non-sleep state or a sleep state, and determine latencymeasurements with greater accuracy.

User applications running on a communication device can result in avariety of traffic patterns. In one embodiment, some user applicationsrunning on a communication device result in regular activity so that thecommunication device is likely in a non-sleep mode. If an agent measureslatency during such a time, injecting artificial traffic to cause thedevice to be in a non-sleep state may be unnecessary. In one embodiment,some user applications may cause the communication device to enter asleep state for periods of time. For example, if a communication deviceruns an application which does not require a large bandwidth, thecommunication device can be configured to enter a sleep state in betweenreceipt and/or transmission of data for the application.

According to one embodiment, an agent measures the behavior of latencyfor an application. In one such embodiment, the agent generates anartificial traffic stream that has the statistical characteristics ofthe application, and measures latency at the moments that are ofinterest for evaluating user experience of using the application. Thus,latency can be measured at time moments that are chosen relative to thetraffic pattern. For the example above where a communication device runsan application which does not require a large bandwidth, an agent cangenerate traffic similar to the application, allowing for thecommunication device to enter a sleep state for periods of time. Latencyof a communication link can be measured at various times during thegenerated traffic, for example, at times when the communication devicemay be in a sleep state.

If the latency is large even after accounting for the power-managementstate of a target communication device, it indicates that the link maynot be healthy (e.g., due to frequent packet losses, packet re-sends,transmission back-off because of the nature of wireless system where thecommon medium air is shared, or other causes of large latency). Whensuch a large latency is detected, a corrective measure such asconfiguration optimization may be desired and can be triggered.Configuration optimizations are discussed in greater detail below withrespect to FIGS. 1a -1 c.

In one embodiment, by detecting and/or avoiding sleep states, systemsand methods determine the latency of communication links with greateraccuracy.

Embodiments include systems and methods for determining connectivitydiagnostics of communication links. In one embodiment, connectivitydiagnostics of the communication link can be determined withoutrequiring availability of testing software applications on both sides ofa communication link. In one embodiment, an operational parameterrelated to the communication link is used to diagnose connectivity.Communication devices, such as Wi-Fi access points (APs) or customerpremise equipment (CPEs), provide operational parameters (OPs) (e.g.,operational parameters 110 of FIGS. 1a and 1b , and operationalparameters 110 a-110 n of FIG. 1c ) as a byproduct of normal systemoperation. According to one embodiment, obtaining and monitoring OPs donot require test traffic to be injected into the network, and thus isnon-intrusive to the user traffic.

One of the available OPs in some communication devices is theassociation-duration for links that are active on that communicationdevice. In one embodiment, this association-duration OP is provided foreach communication link in the form of a time counter. When a systemconnects or reconnects to a target communication device (e.g., when anew active link is established), a new association OP for that specificlink gets instantiated in the target system with the duration countinitialized to zero. The duration counter then starts incrementingcumulatively until the link gets disconnected. Upon link disconnection,the corresponding association OP gets deleted.

In one embodiment, an agent (e.g., an agent within the communicationdevice or external to the communication device) performs fine-grainedmonitoring of connectivity by monitoring the association OPsperiodically and/or frequently (e.g., every one minute on an ongoingbasis, every five minutes for a period of time, or other frequenciesand/or times). According to one embodiment, the agent keeps a record ofthe current active links and their association durations, and frequentlytracks the system OPs to check if the previously recorded links arestill active, if their duration counters are increasing continually,and/or if any new links have been initiated. During this monitoringprocess, the agent observes and can record critical events, including:instantiation events (i.e., the instantiation of an association OP,which identifies a new communication link connection), deletion events(i.e., the deletion of an association OP, which identifies a linkdisconnection), and/or reset events (i.e., instantiation or deletion wasnot recorded, but the counter got reset, which identifies quickreconnection of an existing link that happened between the agentmeasurements).

According to one embodiment, in addition to observing critical events,the agent determines the time of occurrence of critical events and/ortraffic activity during the occurrence of critical events, which canalso be obtained non-intrusively using the OPs.

In one embodiment, the agent uploads the recorded events periodically toa central server, where it is archived for large scale data analysis.The server (e.g., an application running on the server) analyzes, on aperiodical (e.g., hourly, daily, weekly, or other periods of time)basis, one or more statistics for providing connectivity diagnostics forcommunication links. In one embodiment, an agent on the communicationdevice can analyze connectivity events.

According to one embodiment, the agent can determine the total number ofinstantiation, deletion, and reset events. A high count can suggest linkconnectivity issues possibly depending on the correlation with otherstatistics. In another example, the agent determines the averageduration between successive instantiation and deletion events, andbetween successive deletion and instantiation events. Long durationsbetween successive instantiation and deletion events without frequentreset events in between can indicate a stable link, irrespective of thetotal number of events. Long durations between successive deletion andinstantiation events can indicate an inactive link, and the percentageof link inactive periods can be considered for the overall diagnostics.A low number of critical events can indicate that the link was inactivefor long periods of time rather than being unstable. Several resetevents followed by link inactivity could indicate severe connectivityissues, where the communication system has declared that the link isunstable for maintaining connectivity.

According to one embodiment, the time pattern of the critical events canbe analyzed to provide connectivity diagnostics. If the critical eventshappen frequently and contiguously in time, it can indicate connectivityissues. If the critical events are spread apart in time, and/or if thereis a specific time pattern to the occurrence of events, then it couldindicate a certain behavior of the communication device rather than linkconnectivity issues. Examples of communication device behavior that cancreate the critical events include: sleep or other power-saving statesof communication devices, periodic restarts of communication devices,the mobility of wireless devices, channel/radio scan in wirelessdevices, low battery operation, and/or driver issues.

In one embodiment, an analysis server (e.g., management entity) or agentestablishes a baseline trend for a communication link based on timepatterns of the critical events. The server can then distinguish betweencommunication device behavior and actual communication link problems,and diagnose connectivity issues.

According to one embodiment, connectivity diagnostics are performedduring peak hours of network usage, which can more directly correlatewith user experience. An analysis server or agent can correlate times ofinstability with traffic volume and/or patterns.

In one embodiment, an analysis server or agent can refine connectivitydiagnostics by correlation with parameters such as RSSI (Received SignalStrength Indicator), interference, and/or other performance parameters,to determine a root cause of connectivity issues. For example, low RSSIat critical events can indicate disassociation at long range.

In one embodiment, an analysis server or agent can refine connectivitydiagnostics by reading the identification of the communication deviceswhich are being associated to at differing times. For example a Wi-Fistation may be between two APs, and be associating back and forthbetween the two. In another example, the association may alternate tobeing over Wi-Fi and over a cellular network.

According to one embodiment, connectivity diagnostics can be used todirect control actions and/or perform optimizations

In one embodiment, systems and methods enable non-intrusive and light(e.g., not requiring intensive use of memory and/or processor(s)) meansof measuring and estimating the connectivity performance of acommunication link, which can be easily deployed in existing systems.

In the following description, numerous specific details are set forthsuch as examples of specific systems, languages, components, etc., inorder to provide a thorough understanding of the various embodiments. Itwill be apparent, however, to one skilled in the art that these specificdetails need not be employed to practice the disclosed embodiments. Inother instances, well known materials or methods have not been describedin detail in order to avoid unnecessarily obscuring the disclosedembodiments.

The phrases “coupled to,” “coupled with,” connected to,” “connectedwith” and the like are used herein to describe a connection between twoelements and/or components and are intended to mean coupled/connectedeither directly together, or indirectly, for example via one or moreintervening elements or via a wired/wireless connection. References to a“communication system” are intended, where applicable, to includereference to any other type of data transmission system.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus nor are embodimentsdescribed with reference to any particular programming language. It willbe appreciated that a variety of programming languages may be used toimplement the teachings of the embodiments as described herein.

FIGS. 1a-1c illustrate communication networks which are operable todetermine communication link metrics, according to embodiments. Theembodiments in FIG. 1a and FIG. 1b illustrate communication networks 100a and 100 b, which include a first communication device 102communicatively coupled with a second communication device 104 via acommunication link 103. Each of the first communication device and thesecond communication device can be selected from the group of devicesincluding: a cellular telephony compatible device, a third generation(3G) compatible device; a fourth generation (4G) compatible device; aLong Term Evolution (LTE) compatible device; a Wi-Fi device; a Wi-Fiaccess point; a Wi-Fi station; a modem; a router; a gateway; a DigitalSubscriber Line (DSL) Customer Premises Equipment (CPE) modem; anin-home power line device; a Home Phoneline Network Alliance (HPNA)based device; an in-home coax distribution device; a G.hn compatibledevice; an in-home metering communication device; an in-home appliancecommunicatively interfaced with the LAN; a wireless femtocell basestation; a wireless picocell base station; a wireless small-cell basestation; a wireless compatible base station; a wireless mobile devicerepeater; a wireless mobile device base station; an Ethernet gateway; acomputing device connected to the LAN; a HomePlug device; an IEEE P1901standards compatible access Broadband over Power Line (BPL) device; anEthernet connected computer peripheral device; an Ethernet connectedrouter; an Ethernet connected wireless bridge; an Ethernet connectednetwork bridge; and an Ethernet connected network switch.

Communication network 100 b also includes an optimization center 106communicatively coupled with the first communication device 102 viacommunication link 109. FIG. 1c illustrates a communication network 100c, which includes one or more first communication devices 102 a-102 n,which may be communicatively coupled with one or more secondcommunication devices 104 a-104 m via communication links 103 aa-103 nm,where ‘n’ and ‘m’ are positive integers. Communication network 100 cincludes an optimization center 106, which may be coupled with one ormore communication devices 102 a-102 n via communication links 109 a-109n. Communication network 100 c also includes cellular system 112 (e.g.,a 3G/4G system) which can be communicatively coupled with the secondcommunication devices 104 a-104 m via communication links 107 a-107 m.

In one embodiment, the first communication devices 102, and 102 a-102 ncan include: an access point (AP); a base station; a wireless local areanetwork (LAN) device; a Digital subscriber line access multiplexer(DSLAM); a gateway; a performance enhancement device; a DigitalSubscriber Line (DSL) CPE modem; an in-home powerline device; a HomePhoneline Network Alliance (HPNA) based device; an in-home coaxdistribution device; a G.hn (Global Home Networking Standard) compatibledevice; an in-home metering communication device; an in-home appliancecommunicatively interfaced with the LAN; a wireless femtocell basestation; a wireless Wi-Fi compatible base station; a wireless mobiledevice repeater; a wireless mobile device base station; nodes within anad-hoc/mesh network; an set-top box (STB)/set-top unit (STU) customerelectronics device; an Internet Protocol (IP) enabled television; an IPenabled media player; an IP enabled gaming console; an Ethernet gateway;a computing device connected to the LAN; an Ethernet connected computerperipheral device; an Ethernet connected router; an Ethernet connectedwireless bridge; an Ethernet connected network bridge; and/or anEthernet connected network switch. In one embodiment, the firstcommunication devices 102, and 102 a-102 n include operationalparameters 110, and 110 a-110 n, which can be retrieved to aid indetermining communication link metrics, as described below. In oneembodiment, the second communication devices 104 and 104 a-104 m areWi-Fi stations.

In some embodiments, the following may describe operations performed byan agent. The agent referred to can reside in one of the communicationdevices (e.g., agents 108, and 108 a-108 n of FIGS. 1a-1c ), or externalto the communication devices. For example, the agent referred to canreside in the optimization center 106, or in another external entity. Inone embodiment, operations referred to as performed by the agent arepartially performed by an agent in one of the communication devices, andpartially performed by an agent external to the communication devices(e.g., by the optimization center 106). In one such embodiment, agents108, and 108 a-108 n send relevant data to the optimization center 106,and the optimization center 106 performs analysis on the data. Theoptimization center 106 of FIGS. 1b and 1c is a computing device (e.g.,a server, management entity, and/or other entity operable to performoptimizations for communication devices.

In one embodiment, the communication networks 100 a-100 c are operableto determine latency of the communication links 103, and 103 aa-103 nm,and/or determine connectivity metrics for the communication links 103,and 103 aa-103 nm. Although some of the following paragraphs regardinglatency and connectivity metric determinations may refer to a singlefirst communication and a single second communication device coupled viaa single communication link (e.g., as illustrated in the communicationnetwork 100 a of FIG. 1a and communication network 100 b of FIG. 1b ),the following description can also apply to an embodiment such as thecommunication network 100 c illustrated in FIG. 1c with one or morefirst communication devices 102 a-102 n, and one or more secondcommunication devices 104 a-104 m.

In one embodiment where the communication networks 100 a and 100 b areoperable to determine the latency of the communication link 103, thecommunication networks 100 a and 100 b are operable to detect a sleepstate of the second communication device 104 during the latencymeasurements, and/or prevent the second communication device 104 frombeing in a sleep state during latency measurements. For example, thefirst communication device 102 is operable (e.g., via the agent 108) todetermine a power-management state of the second communication device104. In one embodiment, possible power-management states of the secondcommunication device include a sleep state and a non-sleep state.

In one embodiment, the power-management state of the secondcommunication device 104 is a power-management state of a communicationinterface of the second communication device 104. In one embodiment, thepower-management state of the second communication device 104 is apower-management state of any component of the second communicationdevice 104 that influences latency measurement.

According to one embodiment, the first communication device 102 is totransmit one or more packets to the second communication device 104 overthe communication link 103, the one or more packets to be received bythe second communication device 104 while in the power-management state.In one embodiment, the first communication device 102 injects a set ofpackets for making multiple latency measurements. The firstcommunication device 102 is to receive, from the second communicationdevice over the communication link, one or more response packets inresponse to the one or more packets. The first communication device 102determines the latency of the communication link 103 when the secondcommunication device 104 is in the power-management state based on theone or more packets and the one or more response packets.

In one embodiment, determining the latency of the communication link 103includes measuring a time from when the one or more packets aretransmitted to the second communication device 104 to when thecorresponding one or more response packets are received by the firstcommunication device 102. One or more latency measurements can be madebased on the multiple packets transmitted to the second communicationdevice 104 for measuring latency and corresponding response packets.

According to one embodiment, the one or more packets transmitted by thefirst communication device 102 are ICMP echo request packets, and theone or more response packets transmitted by the second communicationdevice 104 are ICMP response packets. For example, Ping, a softwareapplication/method to measure the round-trip time (RTT) between devicescan be used. Ping requires both sender and receiver devices to have thesoftware available at the application layer. Ping uses ICMP packets andreports average, minimum and maximum RTT in addition to RTT of eachpacket. Ping is included and made available in many operating systems(OS's).

In one embodiment, the one or more packets transmitted by the firstcommunication device 102 are TCP Sync (SYN) packets sent to anunreachable port of the second communication device 104, and the one ormore response packets transmitted by the second communication device 104are TCP Reset (RST) packets. For example, the first communication device102 intentionally sends a TCP SYN packet to an unreachable port ofsecond communication device 104. When the TCP SYN packet is blocked, atdefault the receiver sends a TCP RST packet unless it is configuredotherwise. Therefore, the RTT duration between the time the TCP SYNpacket is sent to the time the TCP RST packet is received can be used tomeasure latency. In one embodiment, TCP SYN/RST packets can be used tomeasure latency in communication devices where the underlying MAC layersupports TCP and the firewall setting does not block such TCP SYNpackets.

According to one embodiment, determining the power-management state ofthe second communication device 104 involves injecting traffic to causethe second communication device 104 to be in a non-sleep state for thelatency measurement. For example, determining the power-management stateof the second communication device 104 includes determining the secondcommunication device 104 is in a non-sleep state after transmitting oneor more initial packets to the second communication device 104, whereinthe one or more initial packets cause the second communication device104 to transition to a non-sleep state when received in a sleep state,and to remain in the non-sleep state when received in the non-sleepstate.

In one embodiment, instead of first injecting traffic to cause thesecond communication device 104 to be in a non-sleep state, the firstcommunication device 102 detects which power-management state the secondcommunication device 104 is in, and measures the latency of thecommunication link 103 in that power-management state. For example, inone embodiment, determining the power-management state of the secondcommunication device 104 includes retrieving status information of thesecond communication device 104. The status information can be availablein communication device 102 (e.g., in a Wi-Fi system according to theimplementation in the IEEE 802.11 standard). The status informationretrieved can include operational parameters indicating whether thesecond communication device 104 is in a sleep state or a non-sleepstate, and/or other operational parameters.

In one embodiment, the communication networks 100 a and 100 b areoperable to both inject traffic to influence whether the secondcommunication device 104 is in a non-sleep state or a sleep state, andto retrieve status information to aid in determining whether the secondcommunication device 104 is in a non-sleep state or a sleep state.

In one embodiment, the communication networks 100 a and 100 b arefurther operable to determine latency characteristics of thecommunication link 103 based on multiple latency measurements andmultiple determinations of the power-management state of the secondcommunication device 104. Latency characteristics are, for example,statistics based on multiple latency measurements. Multiple latencymeasurements can be averaged or otherwise combined. In one embodiment,some of the latency measurements are discarded based on thepower-management state of the second communication device 104 at thetime of measurement. For example, if latency measurements not influencedby sleep states are desired, latency measurements made when the secondcommunication device 104 is in a sleep state are discarded.

In one embodiment, the communication device 102 transmits the one ormore packets to generate a traffic stream having statisticalcharacteristics. For example, the communication device 102 or any otherexternal server or device can generate a traffic stream havingstatistical characteristics of particular applications (e.g., userapplications). In one such embodiment, determining latencycharacteristics of the communication link 103 with the traffic stream isbased on multiple latency measurements and multiple determinations ofthe power-management state of the second communication device 104 whilethe traffic stream continues.

Thus, in one embodiment, a method and system for determining latency ofcommunication links between communication devices results in latencymeasurements with greater accuracy.

In one embodiment where the communication networks 100 a and 100 b areoperable to determine a connectivity metric of the communication link103, an agent queries the first communication device 102 at successivetimes to read operational parameters at those times. For example, theagent queries the first communication device 102 at a first time todetermine whether a second communication device 104 is connected to thefirst communication device 102 and to determine a value of anoperational parameter at the first time. The operational parameter isrelated to the communication link 103 between the second communicationdevice 104 and the first communication device 102. For example, theoperational parameter can be a counter which resets upon connectionand/or disconnection of the communication link 103; a global counter,which exists independently of the connectivity of the secondcommunication device 104 to the first communication device 102; or otheroperational parameters related to the communication link 103.

Examples of counters include: association duration counters whichindicate a connection duration of the communication link 103, trafficcounters which indicate the number of packets and/or size of datatransmitted between the first communication device 102 and the secondcommunication device 104, and a beacon counter indicating a number ofbeacons transmitted by the second communication device 104. In oneembodiment where the operational parameter to query is a beacon counter,the agent determines whether a disconnection event occurred based onboth the value of the beacon counter and the beacon interval value. Thebeacon interval value can be known by the agent, or the agent may querythe first or second communication device to determine the beaconinterval value.

In one embodiment, the agent queries the first communication device 102at a second time to determine whether the second communication device104 is connected to the first communication device 102 and to determinea value of the operational parameter at the second time.

If the second communication device 104 was connected at both the firsttime and second time, and if the operational parameter at the secondtime is inside a range of threshold values, the agent can determine thata disconnection event occurred. For example, the agent determines thesecond communication device 104 disconnected from the firstcommunication device based on detecting the second communication devicewas connected to the first communication device 102 at both the firsttime and the second time, and detecting the value of the operationalparameter at the second time is inside a range of threshold values basedon the operational parameter at the first time. In one embodiment wherethe operational parameter is a counter, a disconnection event can beidentified if the value of the counter at the second time is less thanan expected value, and/or less than the value of the counter at thefirst time. The expected value of the counter at the second time can bedetermined based on the value of the counter at the first time and timeelapsed from the first time to the second time.

Although the above description refers to determining operationalparameters at a first time and a second time, the operational parameterscan be monitored multiple times, and/or continuously. For example, theoperational parameters can be determined on a periodic basis (e.g.,every one second, every five seconds, every one minute, every fiveminutes, or any other periodic basis).

In one embodiment, the agent determines the times of connection anddisconnection events. For example, the agent determines times that thesecond communication device 104 connected to and disconnected from thefirst communication device 102. The agent further determines an averageduration between connection and disconnection events for thecommunication link 103 based on those times (i.e., the times that thesecond communication device 104 connected to and disconnected from thefirst communication device 102).

In one embodiment, the agent determines an average duration betweendisconnection and reconnection events for the communication link 103based on the times of connection and disconnection events (i.e., basedon the times the second communication device 104 connected to anddisconnected from the first communication device 102).

According to one embodiment, the agent detects traffic activityoccurring at times of connection and disconnection events. For example,the agent queries the first communication device 102 to retrieve asecond operational parameter from the first communication device 102indicating traffic activity over the communication link 103. Thedetected traffic activity can be used in diagnosing connectivity issues.

In one embodiment, the communication link 103 is determined to beunstable based on statistical data related to connection anddisconnection events. In one embodiment, the agent diagnosesconnectivity issues for the communication link 103. For example, theagent determines that the communication link 103 is unstable formaintaining connectivity based on traffic activity during disconnectionand reconnection events. In one embodiment, the agent determines thatthe communication link 103 is unstable for maintaining connectivity forthe desired QoE (Quality of User Experience) in response to determiningthat a number of times that the second communication device 104disconnected from and reconnected to the first communication device 102exceed threshold values. According to one embodiment, the agentdetermines the communication link 103 is unstable for maintainingconnectivity based on the average duration between connection anddisconnection events being less than a threshold value.

In one embodiment, the agent identifies a time pattern in secondcommunication device disconnections from and reconnections to the firstcommunication device 102. The agent then determines if the communicationlink 103 is unstable for maintaining QoE based on the time pattern. Forexample, the agent determines the communication link 103 is unstablebased on the second communication device disconnections andreconnections occurring contiguously in time. In one embodiment, theagent identifies a behavior of the second communication device 104resulting in the time pattern, the identified behavior including one of:the second communication device 104 entering a sleep state, the secondcommunication device 104 entering a lower power state, the secondcommunication device 104 periodically resetting, the secondcommunication device 104 exiting a coverage range for connectivity withthe first communication device 102, the second communication device 104performing a channel scan, and/or the second communication device 104having a driver malfunction.

In one embodiment, the agent establishes a baseline behavior of thesecond communication device 104 (e.g., based on identified time patternsof connection and disconnection events). The agent can then determinewhether the communication link 103 is unstable for maintainingconnectivity or QoE based on whether connectivity behavior deviates fromthe baseline behavior of the second communication device 104.

According to one embodiment, the agent queries the first communicationdevice 102 to retrieve a second operational parameter from the firstcommunication device 102, the second operational parameter indicating atleast one of: traffic activity over the communication link, receivedsignal strength, and interference. The agent can then analyze the secondoperational parameter at times of connection events and disconnectionevents and determine whether the disconnection events are caused by acondition indicated in the second operational parameter.

Turning to FIG. 1c , in one embodiment, when there are multiple firstcommunication devices 102 a-102 n available to connect to, the secondcommunication devices 104 a-104 m can roam between the available firstcommunication devices based on their internal roaming algorithm.Querying the first communication devices 102 a-102 n can determine if asecond communication device is frequently connecting back and forthbetween the multiple available choices. One or more of the secondcommunication devices 104 a-104 m may also alternate between connectingto one or more of the first communication devices 102 a-102 n and thecellular system 112. For example, when the first communication devices102 a-102 n are Wi-Fi APs and the second communication devices arestations, the stations can alternate between connecting to two or moreof the Wi-Fi APs, or one or more Wi-Fi AP and the cellular system 112.

In one such embodiment, the agent queries, when the second communicationdevice (e.g., 104 a) disconnects from the first communication device(e.g., 102 a), another of the first communication devices (e.g., 102 n)within a coverage range of the second communication device to determinewhether the second communication device is connected to the other firstcommunication device. The agent can then identify a pattern of timesthat the second communication device connects back and forth between thefirst communication device and the other of the first communicationdevices.

In one embodiment, the second communication device could be alternatingbetween connecting to the first communication device and the cellularsystem 112. In one such embodiment, the agent queries, when the secondcommunication device (e.g., 104 a) disconnects from the firstcommunication device (e.g., 102 a), a cellular system 112 within acoverage range of the second communication device to determine whetherthe second communication device is connected to the cellular system. Theagent can then identify a pattern of times that the station connectsback and forth between the first communication device and the cellularsystem 112.

In one embodiment, one or more parameters of the first communicationdevices 102 and 102 a-102 n can be adjusted based on the determinedlatency and/or connectivity issues of the communication links 103 and103 aa-103 nm. For example, the agent can adjust one or more of: aretransmission parameter, a modulation and coding scheme, a channel, aradio band, channel bonding, a guard interval length, a fragmentationthreshold, a retry limit, a request to send (RTS) parameter and a clearto send (CTS) parameter, a beacon interval, a transmission power, amultiple antenna mode, a preamble setting, a maximum bit rate, and aQuality of Service (QoS) configuration parameter.

In one such embodiment, adjusting one or more parameters of the firstcommunication devices can improve latency and/or connectivity.

FIGS. 2-5 are flowcharts for determining communication link metrics,according to embodiments. Methods 200, 300, 400, and/or 500 may beperformed by processing logic that may include hardware (e.g.,circuitry, dedicated logic, programmable logic, microcode, etc.),software (e.g., instructions run on a processing device to performvarious operations such as interfacing, collecting, generating,receiving, monitoring, diagnosing, determining, measuring, analyzing, orsome combination thereof). In accordance with one embodiment, there is anon-transitory machine-readable storage medium having machine executableinstructions that when accessed by a computer, cause the computer toperform a method in accordance with one or more of methods 200, 300,400, and/or 500.

In one embodiment, methods 200, 300, 400, and/or 500 are performed orcoordinated via an apparatus such as the agent depicted at element 108,the optimization center depicted at element 106 of FIGS. 1a-1c , and/orother entities internal to or external from the communication devicesdescribed herein. Some of the blocks and/or operations listed below areoptional in accordance with certain embodiments. The numbering of theblocks presented is for the sake of clarity and is not intended toprescribe an order of operations in which the various blocks must occur.Additionally, operations from the various flows 200, 300, 400, and/or500 may be utilized in a variety of combinations, including incombination with each other.

FIG. 2 is a flowchart for determining the latency of a communicationlink, according to one embodiment. Method 200 begins with a firstcommunication device (e.g., first communication device 102 of FIG. 1a )determining a power-management state of a second communication device(e.g., second communication device 104 of FIG. 1a ), as set forth atblock 201.

At block 202, the first communication device transmits one or morepackets to the second communication device, the one or more packets tobe received by the second communication device while in thepower-management state.

At block 203, the first communication device receives, from the secondcommunication device over the communication link, one or more responsepackets in response to the one or more packets.

At block 204, the first communication device determines a latency of thecommunication link when the second communication device is in thepower-management state based on the one or more packets and the one ormore response packets.

In accordance with one embodiment, a management entity (e.g.,optimization center 106 of FIGS. 1b and 1c ) causes the firstcommunication device to perform one or more of the above operations. Forexample, in one embodiment there is a non-transitory machine-readablestorage medium having machine executable instructions that when accessedby a computer (e.g., an external management entity), cause the computerto perform a method, the method including: sending instructions to afirst communication device to cause the first communication device to:determine a power-management state of a second communication device; andtransmit one or more packets to the second communication device over acommunication link, the one or more packets to be received by the secondcommunication device while in the power-management state; wherein thefirst communication device is to receive, from the second communicationdevice over the communication link, one or more response packets inresponse to the one or more packets; the method to further includedetermining a latency of the communication link when the secondcommunication device is in the power-management state based on the oneor more packets and the one or more response packets.

FIG. 3 is a flowchart for determining the latency of a communicationlink, including transmitting one or more initial packets to acommunication device over a communication link, according to oneembodiment.

Method 300 begins at block 301, with a first communication device (e.g.,first communication device 102 of FIG. 1a ) transmitting one or moreinitial packets to a second communication device (e.g., secondcommunication device 104 of FIG. 1a ). The one or more initial packetscause the second communication device to transition to a non-sleep statewhen received in a sleep state, and to remain in the non-sleep statewhen received in the non-sleep state.

Method 300 continues in blocks 302-304 as method 200 in blocks 202-204of FIG. 2. At block 302, the first communication device transmits one ormore packets to the second communication device, the one or more packetsto be received by the second communication device while in thepower-management state.

At block 303, the first communication device receives, from the secondcommunication device over the communication link, one or more responsepackets in response to the one or more packets.

At block 304, the first communication device determines a latency of thecommunication link when the second communication device is in thepower-management state based on the one or more packets and the one ormore response packets.

FIG. 4 is a flowchart for determining the latency of a communicationlink, including retrieving status information of a communication device,according to one embodiment.

Method 400 begins at block 401, with a first communication device (e.g.,first communication device 102 of FIG. 1a ) retrieving statusinformation indicating whether a second communication device (e.g.,second communication device 104 of FIG. 1a ) is in a sleep state or anon-sleep state.

Method 400 continues in blocks 402-404 as method 200 in blocks 202-204of FIG. 2 and method 300 in blocks 302-304 of FIG. 3. At block 402, thefirst communication device transmits one or more packets to the secondcommunication device, the one or more packets to be received by thesecond communication device while in the power-management state.

At block 403, the first communication device receives, from the secondcommunication device over the communication link, one or more responsepackets in response to the one or more packets.

At block 404, the first communication device determines a latency of thecommunication link when the second communication device is in thepower-management state based on the one or more packets and the one ormore response packets.

FIG. 5 is a flowchart for determining a connectivity metric of acommunication link, according to one embodiment.

Method 500 begins at block 501, with querying a first communicationdevice (e.g., first communication device 102 of FIG. 1a ) at a firsttime to determine whether a second communication device (e.g., secondcommunication device 104 of FIG. 1a ) is connected to the firstcommunication device and to determine a value of an operationalparameter at the first time. The operational parameter is related to acommunication link between the second communication device and the firstcommunication device. Querying the first communication device can beperformed by a management entity within the first communication device(e.g., agent 108 of FIG. 1a ) or external to the first communicationdevice (e.g., optimization center 106 of FIGS. 1b and 1c ).

At block 502, the management entity queries the first communicationdevice at a second time to determine whether the second communicationdevice is connected to the first communication device and to determine avalue of the operational parameter at the second time.

At block 503, the management entity determines the second communicationdevice disconnected from the first communication device based ondetecting the second communication device was connected to the firstcommunication device at both the first time and the second time, anddetecting the value of the operational parameter at the second time isinside a range of threshold values based on the operational parameter atthe first time.

FIG. 6 is a processor-based system 600 in accordance with whichembodiments may operate, be installed, integrated, or configured.

The storage medium 604 and associated computer executable instructions606 may be in any of the communication devices and/or servers discussedherein. The computer-machine-readable/executable instructions 606 areexecuted by a processor 601. Elements of embodiments are provided asmachine-readable medium for storing the computer-executable instructions(e.g., instructions to implement the flowcharts of FIGS. 2-5 and otherprocesses discussed in the description).

In one embodiment, the processor-based system 600 further includes adatabase 602 to store data used by the instructions 606. In oneembodiment, the processor-based system 600 includes a network interface605 to communicate with other devices. In one embodiment, the componentsof the processor-based system 600 communicate with one another via anetwork bus 603.

The machine-readable storage medium 604 may include, but is not limitedto, flash memory, optical disks, hard disk drive (HDD), Solid StateDrive (SSD), CD-Read Only Memory (CD-ROMs), DVD ROMs, RAMs, EPROMs,EEPROMs, magnetic or optical cards, or other type of machine-readablemedia suitable for storing electronic or computer-executableinstructions. For example, embodiments of the disclosure may bedownloaded as a computer program (e.g., BIOS) which may be transferredfrom a remote computer (e.g., a server) to a requesting computer (e.g.,a client) by way of data signals via a communication link (e.g., a modemor network connection).

While the subject matter disclosed herein has been described by way ofexample and in terms of the specific embodiments, it is to be understoodthat the claimed embodiments are not limited to the explicitlyenumerated embodiments disclosed. To the contrary, the disclosure isintended to cover various modifications and similar arrangements aswould be apparent to those skilled in the art. Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements. It is tobe understood that the above description is intended to be illustrative,and not restrictive. Many other embodiments will be apparent to those ofskill in the art upon reading and understanding the above description.The scope of the disclosed subject matter is therefore to be determinedin reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

We claim:
 1. A method comprising: determining, by a first communicationdevice, a power-management state of a second communication device;transmitting, by the first communication device, a plurality of packetsin a continuous stream to the second communication device over acommunication link, the plurality of packets to be received by thesecond communication device while in the power-management state;receiving, from the second communication device over the communicationlink, one or more response packets in response to the transmitting ofthe plurality of packets; and determining a latency of the communicationlink when the second communication device is in the power-managementstate based on the plurality of packets and the one or more responsepackets.
 2. The method of claim 1, wherein each of the firstcommunication device and the second communication device includes oneof: a cellular telephony compatible device a third generation (3G)compatible device; a fourth generation (4G) compatible device; a LongTerm Evolution (LTE) compatible device; a Wi-Fi device; a Wi-Fi accesspoint; a Wi-Fi station; a modem; a router; a gateway; a DigitalSubscriber Line (DSL) Customer Premises Equipment (CPE) modem; anin-home power line device; a Home Phoneline Network Alliance (HPNA)based device; an in-home coax distribution device; a G.hn compatibledevice; an in-home metering communication device; an in-home appliancecommunicatively interfaced with the LAN; a wireless femtocell basestation; a wireless picocell base station; a wireless small-cell basestation; a wireless compatible base station; a wireless mobile devicerepeater; a wireless mobile device base station; an Ethernet gateway; acomputing device connected to the LAN; a HomePlug device; an IEEE P1901standards compatible access Broadband over Power Line (BPL) device; anEthernet connected computer peripheral device; an Ethernet connectedrouter; an Ethernet connected wireless bridge; an Ethernet connectednetwork bridge; or an Ethernet connected network switch.
 3. The methodof claim 1, wherein determining the latency of the communication linkcomprises measuring a time from when the plurality of packets aretransmitted to the second communication device to when the correspondingone or more response packets are received by the first communicationdevice.
 4. The method of claim 1, wherein determining thepower-management state of the second communication device comprises:determining the second communication device is in a non-sleep stateafter transmitting one or more initial packets to the secondcommunication device, wherein the one or more initial packets cause thesecond communication device to transition to a non-sleep state whenreceived in a sleep state, and to remain in the non-sleep state whenreceived in the non-sleep state.
 5. The method of claim 4, wherein thenon-sleep state of the second communication device is a non-sleep stateof a communication interface of the second communication device.
 6. Themethod of claim 1, wherein determining the power-management state of thesecond communication device comprises retrieving status information ofthe second communication device.
 7. The method of claim 6, whereinretrieving the status information of the second communication devicecomprises retrieving status information indicating whether the secondcommunication device is in a sleep state or a non-sleep state.
 8. Themethod of claim 6, wherein retrieving the status information of thesecond communication device comprises retrieving the status informationprior to transmitting the plurality of packets.
 9. The method of claim6, wherein retrieving the status information of the second communicationdevice comprises retrieving the status information after transmittingthe plurality of packets.
 10. The method of claim 6, wherein retrievingthe status information of the second communication device comprisesretrieving the status information prior to and after transmitting theplurality of packets.
 11. The method of claim 1, further comprising:determining latency characteristics of the communication link based onmultiple latency measurements and multiple determinations of thepower-management state of the second communication device.
 12. Themethod of claim 1, wherein transmitting the plurality of packetsgenerates a traffic stream having statistical characteristics, themethod further comprising: determining latency characteristics of thecommunication link with the traffic stream based on multiple latencymeasurements and multiple determinations of the power-management stateof the second communication device while the traffic stream continues.13. The method of claim 1, wherein the plurality of packets are TCP SYNpackets sent to an unreachable port of the second communication device,and wherein the one or more response packets are TCP RST packet.
 14. Themethod of claim 1, wherein the plurality of packets are ICMP echorequest packets, and wherein the one or more response packets are ICMPresponse packets.
 15. The method of claim 1, further comprising:varying, for the first communication device, one or more parametersbased on the determined latency of the communication link, including oneor more of: a retransmission parameter, a modulation and coding scheme,a channel, a radio band, channel bonding, a guard interval length, afragmentation threshold, a retry limit, a request to send (RTS)parameter and a clear to send (CTS) parameter, a beacon interval, atransmission power, a multiple antenna mode, a preamble setting, amaximum bit rate, or a Quality of Service (QoS) configuration parameter.16. A non-transitory machine-readable storage medium having machineexecutable instructions that when accessed by a computer, cause thecomputer to perform a method, the method comprising: sendinginstructions to a first communication device to cause the firstcommunication device to: determine a power-management state of a secondcommunication device; and transmit a plurality of packets in acontinuous stream to the second communication device over acommunication link, the plurality of packets to be received by thesecond communication device while in the power-management state; whereinthe first communication device is to receive, from the secondcommunication device over the communication link, one or more responsepackets in response to the plurality of packets; and determining alatency of the communication link when the second communication deviceis in the power-management state based on the plurality of packets andthe one or more response packets.
 17. The non-transitorymachine-readable storage medium of claim 16, wherein the firstcommunication device is a Wi-Fi access point and the secondcommunication device is a station.
 18. The non-transitorymachine-readable storage medium of claim 16, wherein determining thelatency of the communication link comprises measuring a time from whenthe plurality of packets are transmitted to the second communicationdevice to when the corresponding one or more response packets arereceived by the first communication device.
 19. The non-transitorymachine-readable storage medium of claim 16, wherein determining thepower-management state of the second communication device comprises:determining the second communication device is in a non-sleep stateafter transmitting one or more initial packets to the secondcommunication device, wherein the one or more initial packets cause thesecond communication device to transition to a non-sleep state whenreceived in a sleep state, and to remain in the non-sleep state whenreceived in the non-sleep state.
 20. The non-transitory machine-readablestorage medium of claim 16, wherein the non-sleep state of the secondcommunication device is a non-sleep state of a communication interfaceof the second communication device.
 21. The non-transitorymachine-readable storage medium of claim 16, wherein determining thepower-management state of the second communication device comprisesretrieving status information of the second communication device. 22.The non-transitory machine-readable storage medium of claim 16, whereinretrieving the status information of the second communication devicecomprises retrieving status information indicating whether the secondcommunication device is in a sleep state or a non-sleep state.
 23. Asystem comprising: a first communication device communicatively coupledto a second communication device via a communication link, the firstcommunication device operable to: determine a power-management state ofa second communication device; transmit a plurality of packets in acontinuous stream to the second communication device over thecommunication link, the plurality of packets to be received by thesecond communication device while in the power-management state;receive, from the second communication device over the communicationlink, one or more response packets in response to the plurality ofpackets; and determine a latency of the communication link when thesecond communication device is in the power-management state based onthe plurality of packets and the one or more response packets.
 24. Thesystem of claim 23, wherein each of the first communication device andthe second communication device includes one of: a cellular telephonycompatible device a third generation (3G) compatible device; a fourthgeneration (4G) compatible device; a Long Term Evolution (LTE)compatible device; a Wi-Fi device; a Wi-Fi access point; a Wi-Fistation; a modem; a router; a gateway; a Digital Subscriber Line (DSL)Customer Premises Equipment (CPE) modem; an in-home power line device; aHome Phoneline Network Alliance (HPNA) based device; an in-home coaxdistribution device; a G.hn compatible device; an in-home meteringcommunication device; an in-home appliance communicatively interfacedwith the LAN; a wireless femtocell base station; a wireless picocellbase station; a wireless small-cell base station; a wireless compatiblebase station; a wireless mobile device repeater; a wireless mobiledevice base station; an Ethernet gateway; a computing device connectedto the LAN; a HomePlug device; an IEEE P1901 standards compatible accessBroadband over Power Line (BPL) device; an Ethernet connected computerperipheral device; an Ethernet connected router; an Ethernet connectedwireless bridge; an Ethernet connected network bridge; or an Ethernetconnected network switch.
 25. The system of claim 23, whereindetermining the latency of the communication link comprises measuring atime from when the plurality of packets are transmitted to the secondcommunication device to when the corresponding one or more responsepackets are received by the first communication device.
 26. The systemof claim 23, wherein determining the power-management state of thesecond communication device comprises: determining the secondcommunication device is in a non-sleep state after transmitting one ormore initial packets to the second communication device, wherein the oneor more initial packets cause the second communication device totransition to a non-sleep state when received in a sleep state, and toremain in the non-sleep state when received in the non-sleep state. 27.The system of claim 26, wherein the non-sleep state of the secondcommunication device is a non-sleep state of a communication interfaceof the second communication device.
 28. The system of claim 23, whereindetermining the power-management state of the second communicationdevice comprises retrieving status information of the secondcommunication device.
 29. The system of claim 28, wherein retrieving thestatus information of the second communication device comprisesretrieving status information indicating whether the secondcommunication device is in a sleep state or a non-sleep state.